drm: Remove drm_fb_helper add, add all and remove connector calls

drm_fb_helper_{add,remove}_one_connector() and
drm_fb_helper_single_add_all_connectors() are dummy functions now
and serve no purpose. Hence remove their calls.

This is the preparatory step for removing the
drm_fb_helper_{add,remove}_one_connector() functions from
drm_fb_helper.h

This removal is done using below sementic patch and unused variable
compilation warnings are fixed manually.

@@
@@

- drm_fb_helper_single_add_all_connectors(...);

@@
expression e1;
statement S;
@@
- e1 = drm_fb_helper_single_add_all_connectors(...);
- S

@@
@@

- drm_fb_helper_add_one_connector(...);

@@
@@

- drm_fb_helper_remove_one_connector(...);

Changes since v1:
* Squashed warning fixes into the patch that introduced the
  warnings (into 5/7) (Laurent, Emil, Lyude)

Signed-off-by: Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@intel.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305120434.111091-6-pankaj.laxminarayan.bharadiya@intel.com

drivers/gpu/drm/armada/armada_fbdev.c

@@ -135,12 +135,6 @@ int armada_fbdev_init(struct drm_device *dev)
 		goto err_fb_helper;
 	}
 
-	ret = drm_fb_helper_single_add_all_connectors(fbh);
-	if (ret) {
-		DRM_ERROR("failed to add fb connectors\n");
-		goto err_fb_setup;
-	}
-
 	ret = drm_fb_helper_initial_config(fbh, 32);
 	if (ret) {
 		DRM_ERROR("failed to set initial config\n");